1. Field of the Invention
The present invention relates to extraction of non-ionic organic pollutants absorbed on the surface of a substrate.
2. Description of the Related Art
Non-ionic organic contaminants in the subsurface are absorbed onto naturally occurring organic materials in the soil. Strongly absorbed contaminants are difficult to remove by bioremediation or conventional pump and treat methods. It is desirable to provide an economical and feasible solution for removing absorbed contaminants to reduce environmental risks of soil contamination.
The absorption of surfactants into soil is well documented. (Hand, V. C., and Williams, G. K. "Structure-activity Relationships for Sorption of Linear Alkylbenzenesulfonates", Environ. Sci. Technol., 21(4), 370-373 (1987); Di Toro, D. M., Dodge, L. J., and Hand, V. C. "A Model for Anionic Surfactant Sorption" Environ. Sci. Technol., 24(7), 1013-1020 (1990); Harwell, J. H. "Factors Affecting Surfactant Performance in Groundwater Remediation Applications", Transport and Remediation of Subsurface Contaminants, Sabatini, D. A. and Knox, D. A., eds., ACS Symposium Series 491, American Chemical Society, Washington, DC, 124-132 (1992).
The absorption of non-ionic organic compounds from water to an absorbed surfactant phase has been demonstrated. (Boyd, S. A., Mortland, M. M., and Chiou, C. T. "Sorption Characteristics of Organic Compounds on Hexadecyltrimethylammonium-Smectite" Soil Sci. Soc. Am. J., 52, 652-657 (1988); Valsaraj, K. T. "Partitioning of Hydrophobic Nonpolar Volatile Organics Between the Aqueous and Surfactant Aggregate Phases on Alumina" Sep. Sci. Technol., 24(14), 1191-1205 (1989); Smith, J. A., Jaffe, P. R., and Chiou, C. T. "Effect of Ten Quaternary Ammonium Cations on Tetrachloromethane Sorption to Clay from Water" Environ. Sci. Technol., 24(8), 1167-1172 (1990)).
Efforts directed to the removal of contaminants from water have included utilization of high gradient magnetic separation (HGMS) techniques (Shaikh, A. M. H., and Dixit, S. G. "Removal of Phosphate from Waters by Precipitation and High Gradient Magnetic Separation" Wat. Res., 26(6), 845-852 (1992)). This technique involves precipitation with an appropriate reagent followed by heterocoagulation with a magnetic seed material and removal of the particle aggregate using HGMS.
Moreover, it is known that oxides can be used for the treatment of water contaminated with non-ionic organic compounds. (Scamehorn, J. F., and Harwell, J. H. "Surfactant-based Treatment of Aqueous Streams" Surfactants in Chemical/process Engineering, Wasan, D. T., Ginn, M. E., and Shah, D. O. eds., Marcel Dekker, New York, Vol. I, Chapter 3 (1988); Valsaraj, K. T. "Separation of Hydrophobic Organic Compounds from Wastewater using Surfactant Aggregates on Alumina Particles" Wat. Sci. Tech., 26(5-6), 1213-1220 (1992); Park, J. -W., and Jaffe, P. R. "Development of a Sorbent for Removal of Non-ionic Pollutants from Water" Environmental Engineering: Proceedings of the 1991 Specialty Conference, Am. Soc. Civ. Eng., 248-253 (1991)). Oxide particles having a positively charged surface at the pH of typical natural waters absorb anionic surfactants from solution onto their surface. The resultant oxide has a hydrophophobic surface into which non-ionic organic pollutants will partition.